Chelating compounds and their use

ABSTRACT

A chelating compound of the formula: 
     
         (R--NHOC--CH.sub.2).sub.n --A--(CH.sub.2 COOH).sub.m       (I) 
    
     wherein R is an aromatic ring-containing organic group, A is a residue of an aminopolyacetic acid excluding acetic acid groups (--CH 2  COOH) therefrom, m is an integer of at least two and n is an integer of 1 or 2, or its salt, which has a specificity to a hepatobiliary system so that a complex formed between said chelating compound and a metallic element through a coordinate bond is useful and a diagnostic or therapeutic agent for hepatobiliary organs and tissues.

This is a divisional of copending application Ser. No. 07/682,080, filedApr. 9, 1991.

The present invention relates to chelating compounds and their use. Moreparticularly, it relates to chelating compounds having a chelatingproperty and a specificity or selectivity for a hepatobiliary system,and their use as carriers for metal elements suitable for diagnosis ortherapy of hepatobiliary organs or tissues.

In recent years, patients suffered from diseases in a hepatobiliarysystem such as hepatoma are significantly increased, and it is highlydemanded to establish a reliable diagnostic method, particularly throughimaging, as well as an effective therapeutic method.

Among various imaging agents for hepatobiliary organs or tissues asheretofore reported, there is knowntechnetium-99m-N-pyridoxyl-5-methyltryptophan (Tc-99m-PMT). Imaging withthis complex is well evaluated in showing a significant specificity tohepatocellular carcinoma (Hasegawa et al.: Cancer, 57, 230-236 (1986)).Unfortunately, its sensitivity is however somewhat low as 60%.Diethylenetriaminepentaacetato gadolinium (Gd-DTPA) is also known as anuclear magnetic resonance (NMR) imaging agent (Weinmann et al.: AJR,142, 619-629 (1984)). However, it is excreted into urine so quickly thatits distribution in liver is insufficient and satisfactory informationson liver are hardly obtainable.

As well known, aminopolycarboxylic acids have an excellent chelatingproperty and are useful as carriers for metallic elements suitable fordiagnosis. Thus, the complex formed between aminopoly-carboxylic acidsand metallic elements are used as imaging agents for radioactivediagnosis, nuclear magnetic resonance (NMR) diagnosis, etc.

It has now been found that the introduction of a certain aromaticring-containing organic group into an aminopolycarboxylic acid iseffective in enhancing the specificity or selectivity for ahepatobiliary system. For instance, when DTPA(diethylenetriaminepentaacetic acid) is administered intravenously intoan animal, it is mainly excreted into urine. In contrast, it wasexperimentally confirmed thatN,N''-bis[(2-dansylaminoethyl)carbamoylmethyl]-diethylene-triamine-N,N',N''-triaceticacid (B-DNS-etn-DTPA) obtained by introducing two dansyl groups intoDTPA is excreted mainly into intestine through a hepatobiliary system.

As stated above, aminopolycarboxylic acids are well known chelatingcompounds. Since the coordinate bond formed between aminopolycarboxylicacids and metallic elements are generally stable in an animal or at aphysiological pH range, they are practically used as carriers formetallic elements to make imaging agents, for instance, Gd-DTPA as abovementioned. However, it has never been known that their specificity orselectivity for a hepatobiliary system is significantly enhanced byintroducing a certain aromatic ring-containing organic group therein.

SUMMARY OF THE INVENTION

The present is based on the above finding and provides a chelatingcompound which has a high specificity or selectivity for a hepatobiliarysystem and is useful as a carrier for a metallic element to give adiagnostic or therapeutic agent for hepatobiliary organs and tissues.

The chelating compound of the invention is an aminopolycarboxylic acid,particularly an aminopolyacetic acid, in which one or two carboxylicgroups are each combined with an aromatic ring-containing organic group,particularly through an amide (--CONH--) bond and at least twocarboxylic groups are each kept in a free or salt form to have achelating property with a metallic element.

More specifically, the chelating compound is representable by theformula:

    (R--NHOC--CH.sub.2).sub.n --A--(CH.sub.2 --COOH).sub.m     (I)

wherein R is an aromatic ring-containing organic group, A is a residueof an aminopolyacetic acid excluding acetic acid groups (--CH₂ COOH)therefrom, m is an integer of at least two and n is an integer of atleast one. The carboxyl groups therein may be in a free or salt form.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the scintigram obtained in Example 12.

DETAILED DESCRIPTION OF THE INVENTION

The aminopolyacetic acid comprises a hydrocarbon chain in a straight,branched or cyclic form, at least two amino groups introduced in thehydrocarbon chain (such as --C--NH--C--) and/or at the end of thehydrocarbon chain (such as --C--NH₂), and each of at least three aceticacid groups (--CH₂ --COOH) attached to a nitrogen atom in said aminogroups. For example, such aminopolyacetic acid includesethylenediamine-tetracetic acid (EDTA), diethylenetriamine pentaaceticacid (DTPA), trans-1,2-cyclohexadiamine tetraacetic acid (CyDTA),1,4,7,10-tetraazacyclododecane tetraacetic acid (DOTA), etc. As to otherspecific examples of the aminopolyacetic acid, reference may be made toJP-A-58/29718 (DE-A-3129906).

In the chelating compound of the invention, at least two acetic acidgroups originated from the aminopolyacetic acid are kept in a free orsalt form such as an alkali metal salt so as to capture a metallicelement through a covalent bond, while at least one acetic acid group iscombined with the aromatic ring-containing organic group. Preferably,the aromatic ring-containing organic group is originated from anaromatic ring-containing organic amine, and the combination between theaminopolyacetic acid and the aromatic ring-containing organic amine ismade through a carbonamide (--CONH--) linkage.

As the aromatic ring-containing organic group, there are exemplifiedaryl, alyl(lower)alkyl, arylsulfonyl, aryl(lower)alkylsulfonyl,arylamino(lower)alkyl, aryl(lower)alkylamino(lower)alkyl,arylsulfonylamino(lower)alkyl,aryl(lower)alkylsulfonylamino(lower)alkyl, etc. The aryl portion, ofwhich examples are phenyl, naphthyl, etc., in these groups may beoptionally substituted with lower alkyl (e.g. methyl, ethyl), loweralkylamino (e.g. methylamino, ethylamino), di(lower)alkylamino (e.g.dimethylamino, diethylamino), etc. Thus, specific examples of thearomatic ring-containing organic group represented by the symbol R arephenyl, lower alkylphenyl such as tolyl (e.g. p-tolyl),di(lower)alkylaminophenyl such as dimethylaminophenyl (e.g.p-dimethylaminophenyl), phenyl(lower)alkyl such as phenethyl,benzenesulfonylamino(lower)alkyl such as benzenesulfonylaminoethyl,lower alkylbenzenesulfonylamino(lower)alkyl such astoluenesulfonylaminoethyl (e.g. ptoluenesulfonylaminoethyl),di(lower)alkylaminonaphthalenesulfonylamino(lower)alkyl such asdimethylaminonaphthalenesulfonylaminoethyl ordimethylaminonaphthalenesulfonylaminohexyl, naphthylamino(lower)alkylsuch as naphthylaminoethyl, naphthyl(lower)alkyl such as naphthylmethyl,naphthalenesulfonylamino(lower)alkyl such asnaphthalenesulfonylaminoethyl, etc., among which naphthyl(lower)alkyl,naphthylamino(lower)alkyl, naphthalenesulfonylamino(lower)alkyl,5-dimethylaminonaphthalene-1-sulfonylamino(lower)alkyl (i.e.dansylamino(lower)alkyl), etc. are favorable.

Production of the chelating compound of the invention may be achieved bya per se conventional procedure for formation of an amide bond betweenan amino group and a carboxyl group, for instance, reacting an aromaticring-containing organic amine of the formula: R--NH₂ (wherein R is asdefined above) with an aminopolyacetic acid of the formula:(HOOCCH₂)_(n) --A--(CH₂ COOH)_(m) (wherein A, m and n are each asdefined above) in any reactive form. The reaction may be carried outusually in an inert solvent (e.g. tetrahydrofuran, dioxane,dimethylformamide, benzene, toluene), if necessary, in the presence ofthe agents such as a base, a dehydrating agent, etc. to condense.Depending on the reaction conditions, particularly the proportion of thearomatic ring-containing organic amine to the aminopolyacetic acid,there is produced the desired chelating compound having one or twoaromatic ring-containing organic groups as the major product. When theirmixture is obtained, the mono-substituted product and the bissubstitutedproduct can be easily separated by a per se conventional separationprocedure such as chromatography. In general, the bis-substitutedproduct is favorable, because of its higher specificity or selectivityfor a hepatobiliary system.

The thus obtained chelating compound can be converted into thecorresponding complex by treatment with a metal element in a per seconventional procedure for complexation. The kind of the metal elementmay be appropriately chosen depending on the purpose for which thecomplex is used.

For the nuclear medicine such as scintigraphical diagnosis or radiotherapy, various radioactive metal elements may be used. For instance,the use of such gammaray emitting metal elements as technetium-99m,indium-111 and gallium-67 are preferred in order to produce tumorimagingagents. On the other hand, beta-ray emitting metal elements such asrhenium-186, rhenium-188 and yttrium-90 are clinically useful fortreatment of tumors.

For instance, B-DNS-etn-DTPA as an example of the invention is promptlyexcreted from the normal or healthy liver to bile ducts, but when atumor is present in liver, it is difficulty excreted to bile ducts,because no efficient bile duct exists in the tumor lesion. Utilizingthis dynamic behavior, a complex of B-DNS-etn-DTPA with indium-111 isused as a radioactive imaging agent for diagnosis of a hepatobiliarysystem, and a complex of B-DNS-etn-DTPA with rhenium-186 may be employedto irradiate the tumor lesion in liver for the therapeutic purpose.

Metallic elements usable for NMR imaging are required to beparamagnetic, and their preferred examples are lanthanoid elements underAtomic Nos. 57 to 70 and transition metal atoms under Atomic Nos. 21 to29, 42 and 44. Among them, gadolinium, dysprosium, etc. are especiallypreferred because of their strong magnetic moment and chemicalstability. These paramagnetic metallic elements are often toxic inconcentrations required for NMR imaging, and therefore their amounts tobe introduced into animals are desired to be kept as little as possible.The administration of those paramagnetic metallic elements in the formof complexes with the chelating compounds of the invention is quiteadvantageous, because the toxicity of the metallic elements aresuppressed by the complexation and also their amounts to be administeredfor effective NMR imaging are lowered due to their specificity assuringan efficient accumulation at the target organ or tissue in ahepatobiliary system.

For instance, diethylenetriamine-pentaacetato gadolinium(III) (Gd-DTPA)is normally administered on the clinical use by intravenous injection ata dose of 100 μmol/kg. Since its distribution is not however specificfor a hepatobiliary system, the excretion into urine is made promptly.As the result, sufficient contrast useful for diagnosis can be obtainedonly over a period of time producing the differences in concentrationamong tissues or organs. In fact, the administration of Gd-DTPA to ratsat a dose of 50 μmol/mg does not produce any change of signal intensityin liver (Kawamura et al.: Image Information, 21, 206-207 (1989)).Administration of a complex of Gd(III) withN-[(2-dansylaminoethyl)carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraaceticacid (Gd(III)-DNS-etn-DTPA) to rats produces enhancement of the T₁relaxation in liver even at such a small dose as 20 μmol/kg, and thiseffect remains for one hour after the administration. Thus,Gd(III)-DNS-etn-DTPA is specifically taken up into liver so thatsatisfactory NMR imaging can be obtained even at a low dose.

When the use for X-ray diagnosis is aimed at, the chelating compound ofthe invention may be complexed with a metallic element from Atomic Nos.57 to 83, particularly lanthanum to form a complex.

Practical and presently preferred embodiments of the invention areillustratively shown on the following Examples.

EXAMPLE 1

Preparation ofN-[(2-dansylaminoethyl)carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraaceticacid (DNS-etn-DTPA)(2) andN,N''-bis[(2-dansylaminoethyl)carbamoylmethyl]-diethylenetriamine-N,N',N''-triaceticacid (B-DNS-etn-DTPA)(3):

A. N-Dansyl-ethylenediamine (1) ##STR1##

To a solution of ethylenediamine (635 mg, 10.6 mmol) in chloroform (10ml), a solution of dansyl chloride (285 mg, 1.06 mmol) in chloroform (12ml) was dropwise added, and the reaction mixture was stirred at roomtemperature overnight, followed by addition of a bit of 1 N sodiumhydroxide thereto for hydrolysis of unreacted dansyl chloride. Thereaction mixture was concentrated, and the residue was combined withacetone. Insoluble materials were removed by filtration, and thefiltrate was concentrated. Water (50 ml) was added to the residue, andextracted with ethyl acetate three times. The organic layer was driedover anhydrous sodium sulfate and concentrated. The residue wasdissolved in a small amount of ethyl acetate, a bit of n-hexane wasadded thereto, and the resultant mixture was allowed to stand at roomtemperature overnight. The precipitate was collected and recrystallizedfrom ethyl acetate to give Compound (1) (124 mg). Yield, 63 %.

B. DNS-etn-DTPA (2) and B-DNS-etn-DTPA (3) ##STR2##

Diethylenetriamine-N,N,',N',N'',N''-pentaacetic acetic anhydride (DTPA)(1.39 g, 3.89 mmol) was dissolved in dimethylformamide (30 ml) withheating, and the resultant solution was cooled to room temperature. Asolution of Compound (1) (113 mg, 0.385 mmol) in dimethylformamide (5ml) was dropwise added thereto with stirring, and the reaction wascarried out at room temperature for 1.5 hours. After concentration, theresidue was combined with 0.1 M carbonate buffer (pH 9.0, 20 ml) andcarried out on anionic resin exchange chromatography (resin: AG-X4;eluent: 0.3-3M formic acid) and thin layer chromatography (supportinglayer: silica gel 60; developing solvent: ethanol/ aqueous ammonia=4/1)for purification, whereby Compound (2) (69 mg) and Compound (3) (72 mg)respectively in yields of 27% and 20%.

Compound (2): IR (KBr) cm⁻¹ : SO₂ --NH (1140, 1320), COO⁻ (1400, 1590),CO--NH (1660, 3420), C₁₀ H₆ --N--(CH₃)₂ (2800), CH₂ (2950).

FAB-MS (negative): m/z 667 (M-H)⁻, 689 (M+Na-2H)⁻, m/z 711 (M+2Na-3H)⁻.

Elemental analysis for C₂₈ H₃₈ N₆ O₁₁ S₁ Na₂ ·41/2H₂ O(%): Calcd.: C,42.37; H, 5.97; N, 10.59; S, 4.04. Found: C, 41.94; H, 5.70; N, 10.99;S, 4.06.

Compound (3): IR (KBr) cm⁻¹ : SO₂ --NH (1140, 1320), COO⁻ (1410, 1590),CO--NH (1660, 3400), C₁₀ H₆ --N--(CH₃)₂ (2800), CH₂ (2950).

FD-MS: m/z 945 (M+H).

Elemental analysis for C₄₂ H₅₄ N₉ O₁₂ S₂ Na₃ ·8H₂ O (%): Cacld.: C,43.71; H, 6.11; N, 10.92; S, 5.56. Found: C, 43.54; H, 5.52; N, 10.51;S, 5.89.

EXAMPLE 2

Preparation ofN-[(6-dansylaminohexyl)carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraaceticacid (DNS-hxn-DTPA)(5) andN,N''-bis[(6-dansylaminohexyl)carbamoylmethyl]-diehtylenetriamine-N,N,,N''-triaceticacid (B-DNS-hxn-DTPA)(6):

A. N-Dansyl-hexamethylenediamine (4) ##STR3##

Hexamethylenediamine (5.39 g, 45.9 mmol) was combined withdimethylformamide (15 ml), and a solution of dansyl chloride (2.40 g,8.7 mmol) in dimethylformamide (10 ml) was dropwise added thereto,followed by stirring at room temperature for 4 hours. Insolublematerials were removed by filtration, and the filtrate was stirred atroom temperature overnight. After concentration, water and ethyl acetatewere added to thereto, and 1 N hydrochloric acid was added thereto toadjust the aqueous layer to pH 4. The aqueous layer was washed withethyl acetate three times, adjusted to pH 11 with potassium carbonateand extracted with ethyl acetate twice. The extracts were collected,washed with water three times, dried over anhydrous sodium sulfate andconcentrated to give Compound (4) (1.04 g) as an oil. Yield, 34%.

B. DNS-hxn-DTPA (5) ##STR4##

DTPA anhydride (777 mg, 2.18 mmol) was dissolved in dimethylformamide(20 ml) under heating, and the resultant solution was cooled to roomtemperature. A solution of Compound (4) (130 mg, 0.372 mmol) indimethylformamide (5 ml) was dropwise added thereto with stirring, andthe reaction was carried out at room temperature for 1 hour. Afterconcentration, the residue was combined with 1 M carbonate buffer (pH9.0, 50 ml) and allowed to stand in a refrigerator overnight. Insolublematerials were removed by filtration, and the filtrate was treated inthe same manner as in Example 1 B. to give Compound (5) (47 mg). Yield,17 %.

Compound (5): IR (KBr) cm⁻¹ : SO₂ --NH (1140, 1320), COO⁻ (1410, 1590),CO--NH (1660, 3420), C₁₀ H₆ --N--(CH₃)₂ (2800), CH₂ (2950).

FAB-MS (negative): m/z 745 (M+Na--2H)⁻, m/z 761 (M+K-2H)⁻, m/z 767(M+2Na-3H)⁻, m/z 783 (M+Na+K-3H)⁻.

Elemental analysis for C₃₂ H₄₆ N₆ O₁₁ S₁ Na₂ ·6H₂ O (%): Calcd.: C43.83; H, 6.67; N, 9.58; S, 3.66. Found: C, 43.24; H, 6.43; N, 10.35; S,3.73.

C. B-DNS-hxn-DTPA (6) ##STR5##

The insoluble materials as removed in the above B were collected anddissolved in methanol. The resultant solution was concentrated, and theresidue was carried out on thin layer chromatography for purification,whereby Compound (6) (24 mg) was obtained. Yield, 6%.

Compound (6): IR (KBr) cm⁻ : SO₂ --NH (1140, 1310), COO⁻ (1400, 1580),CH₂ (1450, 2930), ##STR6## CO--NH (1660 3400), C₁₀ H₆ --N--(CH₃)₂(2780).

FAB-MS (negative): m/z 1054 (M-H)⁻, m/z 1076 (M+Na-2H)⁻, m/z 1092(M+K-2H)⁻.

Elemental analysis for C₅₀ H₇₁ N₉ O₁₂ S₂ Na₂ ·7H₂ O (%): Calcd.: C,48.97; H, 6.99; N, 10.28; S, 5.23. Found: C, 48.56; H, 6.44; N, 10.01;S, 5.05.

EXAMPLE 3

Preparation ofN-[[2-(1-naphthylamino)ethyl]carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraaceticacid (8):

A. N-1-Naphthylethylenediamine (7) ##STR7##

To a suspension of N-1-naphthylethylenediamine dihydrochloride (746 mg,2.88 mmol) in chloroform (50 ml), a saturated solution of sodiumhydrogen carbonate (50 ml) was added, and the resultant mixture wasstirred. The organic layer was collected, washed with a saturatedsolution of sodium chloride twice, dried over anhydrous sodium sulfateand concentrated to give Compound (7) (310 mg) as an oil. Yield, 58%.

B.N-[[2-(1-Naphthylamino)ethyl]carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraaceticacid (8) ##STR8##

DTPA anhydride (2.02 g, 5.60 mmol) was dissolved in dimethylformamide(20 ml) with heating and cooled to room temperature. A solution ofCompound (7) (218 mg, 1.17 mmol) in acetone (5 ml) was added theretowith stirring, and the reaction was carried out at room temperature for1.5 hours. The resultant mixture was allowed to stand at roomtemperature in a dark box overnight. The reaction mixture was treatedwith activated charcoal and concentrated. To the residue, 0.1 Mcarbonate buffer (pH 8.9, 20 ml) was added, and the resultant mixturewas treated with activated charcoal, followed by concentration. Theresidue was dissolved in 0.1 M carbonate buffer (pH 8.9, 15 ml), treatedwith activated charcoal and carried out on anionic exchange resinchromatography (resin: AG-X4, eluent: 1.2-4.8 M formic acid) and thinlayer chromatography to give Compound (8) (34 mg). Yield, 5%.

Compound (8): IR (KBr) cm⁻¹ : COOC⁻ (1400, 1580), CO--NH (1660, 3400),CH₂ (2960).

FAB-MS (positive): m/z 606 (M+2Na-H)⁺, m/z 622 (M+K+Na-H)⁺, m/z 650(M+4Na-3H)⁺.

Elemental analysis for C₂₆ H₃₃ N₅ O₉ Na₂ ·6H₂ O (%): Calcd.: C, 43.76;H, 6.36; N, 9.81. Found: C, 43.81; H, 6.09; N, 10.58.

EXAMPLE 4

Preparation ofN,N''-bis(1-naphthylmethyl-carbamoylmethyl)-diethylenetriamine-N,N',N'',N''-triaceticacid (9): ##STR9##

DTPA anhydride (2.05 g, 5.74 mmol) was dissolved in hotdimethylformamide (20 ml) with heating and cooled to room temperature. Asolution of 1-naphthalenemethylamine (467 mg, 2.88 mmol) in acetone (5ml) was dropwise added thereto, and the resultant mixture was stirred atroom temperature for 2 hours. After concentration, 0.1 M carbonatebuffer (pH 8.9, 30 ml) was added to the residue. Insoluble materialswere collected, dissolved in methanol with heating and then cooled.After removal of insoluble materials by filtration, the filtrate wasconcentrated. The residue was dissolved in a small amount ofdimethylformamide and carried out on thin layer chromatograph forpurification, whereby Compound (9) (114 mg) was obtained. Yield, 6 %.

Compound (9): IR (KBr) cm⁻¹ : COO⁻ (1400, 1590), ##STR10## (1510, 3050),CO--NH (1650, 3400), CH₂ (2950).

FAB-MS (positive): m/z 710 (M+K)⁺, m/z 732 (M+K+Na-H)⁺, m/z 748(M+2K-H)⁺.

Elemental analysis for C₃₆ H₄₀ N₅ O₈ Na₁ ·5H₂ O (%): Calcd.: C, 55.17;H, 6.43; N, 8.94. Found: C, 54.82; H, 6.08; N, 9.65.

EXAMPLE 5

Preparation ofN-[[2-(1-naphthalenesulfonylamino)carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraacetic acid (11):

A. N-(1-Naphthalenesulfonyl)-ethylenediamine (10) ##STR11##

To a solution of ethylenediamine (1.06 g, 17.6 mmol) indimethylformamide (10 ml), triethylamine (1.79 g, 17.7 mmol) was added,followed by stirring. With stirring at room temperature, a solution of1-naphtalenesulfonyl chloride (4.00 g, 17.6 mmol) in dimethylformamide(15 ml) was dropwise added thereto, and the reaction was carried out inan ice bath for 1 hour. Insoluble materials were removed by filtration,and the filtrate was concentrated. To the residue, chloroform and waterwere added, and insoluble materials were filtered off. Furthermore, theaqueous layer was separated, washed with ethyl acetate twice andadjusted to pH 11 with potassium carbonate, followed by extraction withethyl acetate three times. The extracts were collected, washed withwater twice, dried over anhydrous sodium sulfate and concentrated. Theresidue was allowed to stand in a refrigerator overnight, and theprecipitate was collected and recrystallized from ethyl acetate to giveCompound (10) (153 mg). Yield, 4%.

B.N-[[2-(1-Naphthalenesulfonylamino)ethyl]carbamoylmethyl]-diethylenetriamine-N,N',N'',N''-tetraacetic acid (11) ##STR12##

DTPA anhydride (996 mg, 2.79 mmol) was dissolved in dimethylformamide(20 ml) with heating, and the resultant solution was cooled to roomtemperature. A solution of Compound (10) (139 mg, 0.557 mmol) in acetone(20 ml) was dropwise added thereto at room temperature with vigorousstirring. After the addition, the resultant mixture was stirred at roomtemperature for 1 hour and then allowed to react overnight. Afterconcentration, the residue was dissolved in 0.1 M carbonate buffer (pH8.9, 15 ml) and then treated in the same manner as in Example 1 B togive Compound (11) (66 mg). Yield, 19%.

Compound (11): IR (KBr) cm⁻¹ : SO₂ --NH (1160, 1320), COO⁻ (1400, 1590),CH₂ (2870), CO--NH (3420).

FAB-MS (negative): m/z 646 (M+Na-2H)⁻, m/z 662 (M+K+2H)⁻, m/z 668(M+2Na-3H)⁻, m/z 684 (M+Na+K-3H)⁻.

Elemental analysis for C₂₆ H₃₄ N₅ O₁₁ S₁ ·6H₂ O (%): Calcd.: C, 41.32;H, 6.14; N, 9.27; S, 4.24.

Found: C, 41.05; H, 5.55; N, 9.96; S, 4.23.

From the results of the elemental analysis as above, the products inExamples 1 to 11, i.e. Compounds (2), (3), (5), (6), (8), (9) and (11),were obtained in the form of sodium salt. This is probably due to sodiumsalt in the supporting layer used in thin layer chromatography at thestage of purification.

EXAMPLE 6

In-111-DNS-etn-DTPA (complex):

A. Preparation of In-111 complex with Compound (2)

Compound (2) (0.93 mg, 1.39 μmol) was dissolved in 0.2 M acetate buffer(pH 5.3, 0.46 ml), and the similar buffer (pH 5.3, 0.46 ml) containingindium chloride (¹¹¹ In, 69.1 MBq) was added thereto. The resultantmixture was shaken for 30 seconds to give In-111-DNS-etn-DTPA.

B. Behavior of In-111-DNS-etn-DTPA on thin layer chromatography

An appropriate amount of In-111-DNS-etn-DTPA was spotted onto a silicagel plate (silica gel 60 manufactured by Merck Co., Ltd.) at a distanceof 2 cm from the bottom and developed for 10 cm using a mixture ofmethanol-acetic acid (5 : 3) as a developing solvent. After air-drying,the plate was scanned with a thin layer radiochromatoscanner (Aloca Co.)to determine the distribution of radioactivity, and the radiochemicalpurity was calculated with a data processing apparatus (D-2000,manufactured by Hitachi Ltd.).

As the result, a single radioactivity peak (Rf=0.13) was observed. Sincethe Rf value of this peak is different from that (Rf=0) of indiumacetate (¹¹¹ In) or indium chloride (¹¹¹ In) as a possible radiochemicalimpurity, the radiochemical purity of In-111-DNS-etn-DTPA was determinedto be 100%.

C. Behavior of In-111-DNS-etn-DTPA on electrophoresis

An appropriate amount of In-111-DNS-etn-DTPA was spotted on anacetylated cellulose membrane and subjected to electrophoresis using 50mM phosphate buffer (pH 7.4) with a constant current of 1 mA/cm at roomtemperature for 30 minutes. In the same manner as in the above B, themembrane was scanned with a thin layer radiochromatoscanner to determinethe distribution of radioactivity. As the result, it was revealed thatIn-111-DNS-etn-DTPA is a complex having a single negative charge.

EXAMPLE 7

Other In-111 complexes:

In the same manner as in Example 6 A, B and C, In-111 complexes withCompounds (3), (5), (6), (8), (9) and (11) were prepared, and theirbehaviors on thin layer chromatography (TLC) and electrophoresis (EP) aswell as their radiochemical purity were determined. The results areshown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Carrier                        Radiochemical                                  compound  TLC (Rf)    EP       purity (%)                                     ______________________________________                                        (3)       0.12        --       100                                            (5)       0.14        Negative 100                                            (6)       0.08        --       100                                            (8)       0.19        Negative 100                                            (9)       0.20        Positive 100                                            (11)      0.24        Negative 100                                            ______________________________________                                    

EXAMPLE 8

Gd-DNS-etn-DTPA (complex):

Compound (2) (21.0 mg, 31.4 μmol) was dissolved in 0.2 M acetate buffer(pH 5.3, 5 ml), and 1.97 ml of a 10⁻³ N hydrochloric acid (10.5 ml)containing GdCl₃ ·6H₂ O (93.3 mg, 0.251 mmol) were added thereto. Theresultant mixture was shaken for 1 minute and concentrated. The residuewas dissolved in water (2 ml) and subjected to high performance liquidchromatography for purification, followed by lyophilization to giveGd-DNS-etn-DTPA (20.3 mg). Yield, 79%.

IR (KBr) cm⁻¹ : SO₂ --NH (1150, 1320), COO⁻ (1410, 1590), C₁₀ H₆--N--(CH₃)₂ (2800), CH₂ (2950), CO--NH (3400).

FAB-MS (positive): m/z 823 M⁺, m/z 845 (M+Na-H)⁺.

Elemental analysis for C₂₈ H₃₇ N₆ O₁₁ S₁ Gd₁ ·9H₂ O (%): Calcd.: C,34.1; H, 5.6; N, 8.5; S, 3.3. Gd, 16.0. Found: C, 33.4; H, 4.7; N, 8.4;S, 3.5; Gd, 15.4.

EXAMPLE 9

Eu-DNS-etn-DTPA (complex) and La-DNS-etn-DTPA (complex):

In the same manner as in Example 8 but using EuCl₃ ·6H₂ O or LaCl₃ ·7H₂O, the Eu or La complex with Compund (2) was prepared. There was thusobtained Eu-DNS-etn-DTPA (19.4 mg) in a yield of 77% or La-DNS-etn-DTPA(14.4 mg) in a yield of 61%.

Eu-DNS-etn-DTPA: IR (KBr) cm⁻¹ : SO₂ --NH (1150, 1330), COO⁻ (1410,1600), C₁₀ H₆ --N--(CH₃)₂ (2800), CH₂ (2960), CO--NH (3420).

FAB-MS (negative): m/z 817 (M-H)⁻.

Elemental analysis for C₂₈ H₃₇ N₆ O₁₁ S₁ Eu₁ ·71/2H₂ O (%): Calcd.: C,35.3; H, 5.5; N, 8.8; S, 3.4; Eu, 15.9. Found: C, 35.1; H, 4.6; N, 8.7;S, 4.0; Eu, 15.0.

La-DNS-etn-DTPA: IR (KBr) cm⁻¹ : SO₂ --NH (1150, 1330), COO⁻ (1410,1590), C₁₀ H₆ --N--(CH₃)₂ (2800), CH₂ (2950), CO--NH (3420).

FAB-MS (negative): m/z 803 (M-H)⁻.

Elemental analysis for C₂₈ H₃₇ N₆ O₁₁ S₁ La₁ ·8H₂ O (%): Calcd.: C,35.4; H, 5.6; N, 8.9; S, 3.4; La, 14.6. Found: C, 34.7; H, 4.4; N, 8.7;S, 2.9; La, 13.7.

EXAMPLE 10

Radioactivity distribution of In-111-DNS-etn-DTPA andIn-111-B-DNS-etn-DTPA in rats on intravenous injection:

In-111-DNS-etn-DTPA or In-111-B-DNS-etn-DTPA was intravenously injectedto Sprague-Dawley rats (female) at a dose of 25 μg/rat, and the ratswere sacrificed one hour thereafter to take out various organs. Theradioactivity in each organ was measured, and the results are shown inTable 2.

                  TABLE 2                                                         ______________________________________                                        Radioactivity distribution of In-111-DNS-etn-DTPA                             and In-111-B-DNS-etn-DTPA in rats (% injected                                 dose/organ)                                                                                 In-111-DNS-                                                                              In-111-B-DNS-                                        Organ         etn-DTPA   etn-DTPA                                             ______________________________________                                        Liver         1.35       2.60                                                 Bowel         68.01      91.86                                                Kidney        1.00       0.26                                                 Urinary bladder                                                                             25.49      3.86                                                 Blood (1 ml)  0.06       0.03                                                 Others        7.97       2.74                                                 ______________________________________                                    

From the above results, it is suggested that In-111-B-DNS-etn-DTPA is anexcellent radioactive diagnostic agent for examination of hepatobiliarytissues.

For comparison, the radioactivity distribution of In-111-DTPA (In-111complex with DTPA), prepared as in Example 6 A, in rats on intravenousinjection was determined as above. As the result, it was revealed thatabout 90% of the injected radioactivity was excreted in urine within onehour after the administration.

It is thus found that the excretion route of DTPA is changed to ahepatobiliary system by introduction of a dansyl group therein. In otherwords, a dansyl group may be concluded to be effective in theconstruction of a hapatobiliary tissue-specific carrier.

EXAMPLE 11

Radioactivity distribution of In-111-DNS-hxn-DTPA andIn-111-B-DNS-hxn-DTPA in rats on intravenous injection:

In-111-DNS-hxn-DTPA or In-111-B-DNS-hxn-DTPA was intravenously injectedto Sprague-Dawley rats (female) at a dose of 25 μg/rat, and the ratswere sacrificed one hour thereafter to take out various organs. Theradioactivity in each organ was measured, and the results are shown inTable 3.

                  TABLE 3                                                         ______________________________________                                        Radioactivity distribution of In-111-DNS-hxn-DTPA                             and In-111-B-DNS-hxn-DTPA in rats (% injected                                 dose/organ)                                                                                 In-111-DNS-                                                                              In-111-B-DNS-                                        Organ         hxn-DTPA   hxn-DTPA                                             ______________________________________                                        Liver         0.51       1.82                                                 Bowel         93.42      92.81                                                Kidney        0.05       0.12                                                 Urinary bladder                                                                             5.35       0.46                                                 Blood (1 ml)  0.01       0.05                                                 Others        0.65       4.45                                                 ______________________________________                                    

From the above results, it is found that like In-111-B-DNS-etn-DTPA,tested In-111 complexes are both excellent diagnostic agents forhepatobiliary tissues.

EXAMPLE 12

Imaging of rat hepatoma in rat with In-111-B-DNS-etn-DTPA:

In-111-B-DNS-etn-DTPA was injected into a hepatoma-transplanted WKA-rat(male, tumor size: about 3 cm) intravenously injected at a dose of 50μg/rat and kept in a cage for 70 hours. The rat was fixed and subjectedto image with a gamma-camera (manufactured by Toshiba, Ltd.). Theposterior scintigram thus obtained is shown in FIG. 1 of theaccompanying drawings. While the radioactivity was taken up in liver andbowel, the tumor (at the left shoulder of the rat) was clearlyvisualized.

From the above results, it is clear that In-111-B-DNS-etn-DTPA is takenup into hepatoma.

EXAMPLE 13

A. Relaxation of Gd-DNS-etn-DTPA

Gd-DNS-etn-DTPA as obtained in Example 8 was dissolved in 10 mM acetatebuffer (pH 5.5), and the relaxation time (T₁ and T₂, millisecond) wasmeasured with regard to water proton by NMR (manufactured by NihonDenshi; 270 MHz; 25° C.). The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        Concentration                                                                 (mM)              T.sub.1 T.sub.2                                             ______________________________________                                        5.59               44      36                                                 1.31              313     246                                                 0.66              534     424                                                 0                 3260    1315                                                ______________________________________                                    

From the above results, Gd-DNS-etn-DTPA shows an excellent relaxationtime. For instance, the T₁ and T₂ values of water were shortened about74 times and about 37 times at a concentration of 5.59 mM, respectively.

B. Pharmacodynamics on relaxation of Gd-DNS-etn-DTPA in mice:

To each of ICR mice (female), a solution of Gd-DNS-etn-DTPA in 10 mMacetate buffer (pH 5.5) was intravenously administered at a dose of 0.02mM/kg by injection. The mice were sacrificed by cutting their necks at 1minute, 1 hour and 6 hours after the administration. The protonrelaxation value of each selected organ was measured in a test tube byNMR (270 MHz) at 25° C. Relaxation of T₁ and T₂ on each organ is shownin Table 5.

                  TABLE 5                                                         ______________________________________                                                  Time                                                                Normal      After      After      After                                       value       1 min.     60 min.    360 min.                                    Organ T.sub.1                                                                              T.sub.2                                                                              T.sub.1                                                                             T.sub.2                                                                            T.sub.1                                                                             T.sub.2                                                                            T.sub.1                                                                             T.sub.2                       ______________________________________                                        Liver 1040   17     776   16    745  17   1025  19                            Heart 1484   29     1289  28   1408  26   1523  29                            Kidney                                                                              1269   31     918   28    878  29   1196  33                            Brain 1576   45     1556  --   1586  51   1613  50                            Blood 1755   53     884   --   1713  67   1680  54                            ______________________________________                                    

From the above results, it is revealed that Gd-DNS-etn-DTPA is quicklytaken up by liver, kidney and heart in mouse and excreted. Since thechange of T₁ in liver and kidney with time is distinguished from that ofT₁ in blood, the behavior of Gd-DNS-etn-DTPA in liver and kidney may beconsidered to be not originated from that in blood. Furthermore,Gd-DNS-etn-DTPA may be found to afford an influence on the T₁ relaxationin a living body.

What is claimed is:
 1. A complex which comprises a chelating compoundand a radioactive metallic element coordinately bound thereto, saidchelating compound having the formula:

    (R--NHOC--CH .sub.2).sub.n --A--(CH.sub.2 --COOH).sub.m    (I)

wherein R is naphthyl, naphthyl(lower)alkyl, naphthylsulfonyl,naphthyl(lower)alkylsulfonyl, naphthylamino)lower)alkyl,naphthyl(lower)alkylamino(lower)alkyl, naphthylsulfonylamino(lower)alkylor naphthyl(lower alkylsulfonylamino)lower)alkyl, the naphthyl moietybeing optionally substituted with lower alkyl, lower alkylamino ordi(lower)alkylamino, A is a residue of an aminopolyacetic acid excludingacetic acid groups (--CH₂ COOH) therefrom, m is an integer of at least 2and n is an integer of 1 or 2, or its salt.
 2. The complex according toclaim 1, wherein R is dansyl.
 3. The complex according to claim 1,wherein R is dansylamino(lower)alkyl.
 4. The complex according to claim1, wherein the aminopolyacetic acid comprises a hydrocarbon chain in astraight, branched or cyclic form, at least two amino groups in thehydrocarbon chain, at the terminal position or in the hydrocarbon chainand at the terminal position, and at least three acetic acid (--CH₂COOH) groups attached to the same or different nitrogen atoms in saidamino groups.
 5. The complex according to claim 1, wherein theaminopolyacetic acid is ethylenediamine tetraacetic acid (EDTA),diethylenetriamine pentaacetic acid (DTPA), trans-1,2-cyclohexadiaminetetraacetic acid (CyDTA) or 1,4,7,10-tetraazacyclododecane tetraaceticacid (DOTA).
 6. The complex according to claim 1, wherein theradioactive metallic element is technetium-99m, indium-111, rhenium-186,rhenium-188 or yttrium-90.
 7. A diagnostic agent for hepatobiliaryorgans or tissues which comprises a complex according to claim
 1. 8. Atherapeutic agent for hepatobiliary organs or tissues which comprises acomplex according to claim
 1. 9. A complex which comprises a chelatingcompound and a radioactive metallic element coordinately bound thereto,said chelating compound having the formula

    (R--NHOC--CH.sub.2).sub.n --A--(CH.sub.2 COOH).sub.m       (I)

wherein R is an aromatic ring-containing organic group, A is a residueof an aminopolyacetic acid excluding acetic acid groups (--CH₂ COOH)therefrom, said aminopolyacetic acid being a member selected from thegroup consisting of ethylenediamine tetraacetic acid (EDTA),diethylenetriamine pentaacetic acid (DTPA), trans-1,2-cyclohexadiaminetetraacetic acid (CyDTA) and 1,4,7,10-tetraazacyclododecane tetraaceticacid (DOTA), m is an integer of at least 2 and n is an integer of 1 or2, or its salt.